1. Field of the Invention
The present invention relates to a semiconductor device including a nonvolatile semiconductor memory such as a NAND flash memory and a method for manufacturing the semiconductor device.
2. Description of the Related Art
A nonvolatile semiconductor memory is one of the semiconductor memory devices. In recent years, the nonvolatile semiconductor device is in increasing demand as data storage device. NAND flash memory is known as typical electrically rewritable nonvolatile memory using floating gate (FG) electrode and control gate (CG) electrode.
As the CG electrode of the NAND flash memory, a stacked type electrode comprising a first electrode formed of polycrystalline silicon and a second electrode provided on the first electrode and formed of metal silicide (Jpn. Pat. Appln. KOKAI Publication No. 2-188969).
Device elements have been increasingly miniaturized in order to increase the storage capacity of NAND flash memory. The miniaturization of the device elements increases the aspect ratio of the device element structure. With the CG electrode of the stacked type, it is difficult to inhibit an increase in the aspect ratio of the CG electrode resulting from the miniaturization of the device elements. The reason is as mentioned below. Because the electrode formed of polycrystalline silicon has a higher resistance than the electrode formed of metal silicide, it requires thickening the electrode formed of metal silicide in order to suppress resistance increase caused by miniaturization of the device elements.